To find the square feet of a board; Multiply the length (in feet) by the width (in inches) and divide the result by 12. For example, a 16 foot board that is 9 inches wide would be; 9 x 16 = 144 / 12 = 12 square feet.

To find the number of board feet in a log; Subtract 4 inches from the diameter and square the remainder (multiply by 4). The result will be the number of board feet in a 16 foot log. Add 1/8 for 18-foot logs, 1/4 for 20-foot logs. Subtract 1/8 for 14-foot logs, 1/4 for 12-foot logs.